What pressure (in atm) does 3.54 moles of chlorine gas at 376 K exert in a 51.2 L container?

What you are solving for

You are given the amount of gas, the temperature, and the container volume. For a gas in a sealed container that behaves ideally, pressure is found directly from the ideal gas law.

Plug into the ideal gas law

Use $$P=\frac{nRT}{V}$$ with $n=3.54\,\text{mol}$, $T=376\,\text{K}$, $V=51.2\,\text{L}$, and $R=0.08206\,\frac{\text{L·atm}}{\text{mol·K}}$.

$$P=\frac{(3.54)(0.08206)(376)}{51.2}$$

Compute the pressure

First multiply in the numerator:

$$(0.08206)(376)\approx 30.85$$ $$(3.54)(30.85)\approx 109.22$$

Now divide by the volume:

$$P\approx \frac{109.22}{51.2}\approx 2.13\,\text{atm}$$

Unit check

$\text{mol}$ cancels with $\text{mol}$, and $\text{K}$ cancels with $\text{K}$, leaving $\text{L·atm}/\text{L}=\text{atm}$, so the final unit is correct.